Comparison of the Rodac imprint method to selective enrichment broth for recovery of vancomycin-resistant enterococci and drug-resistant Enterobacteriaceae from environmental surfaces

Factors influencing environmental sampling recovery of healthcare pathogens from non-porous surfaces with cellulose sponges

Results from sampling healthcare surfaces for pathogens are difficult to interpret without understanding the factors that influence pathogen detection. We investigated the recovery of four healthcare-associated pathogens from three common surface materials, and how a body fluid simulant (artificial test soil, ATS), deposition method, and contamination levels influence the percent of organisms recovered (%R). Known quantities of carbapenemase-producing KPC+ Klebsiella pneumoniae (KPC), Acinetobacter baumannii, vancomycin-resistant Enterococcus faecalis, and Clostridioides difficile spores (CD) were suspended in Butterfield's buffer or ATS, deposited on 323cm2 steel, plastic, and laminate surfaces, allowed to dry 1h, then sampled with a cellulose sponge wipe. Bacteria were eluted, cultured, CFU counted and %R determined relative to the inoculum. The %R varied by organism, from <1% (KPC) to almost 60% (CD) and was more dependent upon the organism's characteristics and presence of ATS than on surface type. KPC persistence as determined by culture also declined by >1 log10 within the 60 min drying time. For all organisms, the %R was significantly greater if suspended in ATS than if suspended in Butterfield's buffer (p<0.05), and for most organisms the %R was not significantly different when sampled from any of the three surfaces. Organisms deposited in multiple droplets were recovered at equal or higher %R than if spread evenly on the surface. This work assists in interpreting data collected while investigating a healthcare infection outbreak or while conducting infection intervention studies.

Study of the Effectiveness of Multipurpose Solutions on the Bacterial Disinfection of Silicone Hydrogel Contact Lenses In Vitro

OBJECTIVES

To assess the antimicrobial effectiveness of multipurpose solutions in regard to the disinfection of silicone hydrogel contact lenses (CL) using a study of clinical bacterial isolates from ocular material.

METHODS

Three multipurpose solutions (solution A: polyhexamethylene biguanide 0.00025 g/100 mL; solution B: polyquaternary-1 0.001% and myristamidopropyl dimethylamine 0.0006%; and solution C: polyaminopropyl biguanide 0.00013% and polyquaternary 0.0001%) were used as a 3-phase disinfection on silicone hydrogel CL contaminated with bacteria from clinical isolates that were divided into five groups (group 1: Pseudomonas aeruginosa; group 2: Staphylococcus aureus; group 3: Staphylococcus epidermidis; group 4: Streptococcus spp; and group 5: enterobacteria).

RESULTS

No differences were observed between the 24- and 48-hr measurements in any of the samples, and the positivity of microorganisms in T0 was 100% for all solutions; it was 0% in T3. Therefore, only steps T1 (rubbing followed by rinsing) and T2 (rubbing followed by rinsing and immersion of CL into solution) were considered for analysis at the 24-hr measurement time. Throughout the phases, a decrease in the number of bacteria was observed, culminating in the elimination (no recovery) of all microorganisms in the three solutions.

CONCLUSIONS

At the end of the proposed process, the tested solutions were effective.

Use of RODAC plates to measure containment of Mycobacterium tuberculosis in a Class IIB biosafety cabinet during routine operations

OBJECTIVE/BACKGROUND

Guidelines for the manipulation of Mycobacterium tuberculosis (MTB) cultures require a Biosafety Level 3 (BSL-3) infrastructure and accompanying code of conduct. In this study, we aimed to validate and apply detection methods for viable mycobacteria from surfaces in a BSL-3 MTB laboratory.

METHODS

We evaluated phenotypic (Replicate Organism Detection and Counting [RODAC] plates) and molecular (propidium monoazide [PMA]-based polymerase chain reaction [PCR]) approaches for the detection of viable mycobacteria, as well as the effect of 70% ethanol applied for 5min for disinfection against mycobacteria. For validation of the method, recovery of serial dilutions of Mycobacterium bovis bacillus Calmette-Guérin from glass slides was measured. Subsequently, we stamped surfaces in and around the biosafety cabinet (BSC) after different technicians had manipulated high bacterial load suspensions for routine drug-susceptibility testing in a Class II BSC.

RESULTS

RODAC stamping could detect as few as three bacteria on slides stamped either 5min or 60min after inoculation. PMA-based PCR, tested in parallel, did not pass validation. Mycobacteria were still detected after 5-min disinfection with ethanol 70%. In the BSL-3, from 201 RODAC-stamped surfaces, MTB was detected in four: three inside a BSC-on a tube cap and on an operator's gloves-and one outside, on an operator's gown.

CONCLUSION

RODAC plates detect mycobacteria at low numbers of microorganisms. In addition, this method allowed us to show that 70% ethanol does not reliably kill mycobacteria when applied for 5min to a dried surface, and that MTB bacilli may arrive outside a Class II BSC during routine practice, although the route could not be documented.

Bacterial contamination of healthcare workers' uniforms: a randomized controlled trial of antimicrobial scrubs

BACKGROUND

Healthcare workers' (HCWs) uniforms become contaminated with bacteria during normal use, and this may contribute to hospital-acquired infections. Antimicrobial uniforms are currently marketed as a means of reducing this contamination.

OBJECTIVE

To compare the extent of bacterial contamination of uniforms and skin when HCWs wear 1 of 2 antimicrobial scrubs or standard scrubs.

DESIGN

Prospective, randomized, controlled trial.

SETTING

University-affiliated, public safety net hospital

PARTICIPANTS

Hospitalist physicians, nurse practitioners, physician assistants, housestaff, and nurses (total N = 105) working on internal medicine units.

INTERVENTION

Subjects were randomized to wear standard scrubs or 1 of 2 antimicrobial scrubs.

MEASUREMENTS

Bacterial colony counts in cultures taken from the HCWs' scrubs and wrists after an 8-hour workday.

RESULTS

The median (interquartile range) total colony counts was 99 (66-182) for standard scrubs, 137 (84-289) for antimicrobial scrub type A, and 138 (62-274) for antimicrobial scrub type B (P = 0.36). Colony counts from participants' wrists were 16 (5-40) when they wore standard scrubs and 23 (4-42) and 15 (6-54) when they wore antimicrobial scrubs A and B, respectively (P = 0.92). Resistant organisms were cultured from 3 HCWs (4.3%) randomized to antimicrobial scrubs and none randomized to standard scrubs (P = 0.55). Six participants (5.7%) reported side effects to wearing scrubs, all of whom wore antimicrobial scrubs (P = 0.18).

CONCLUSIONS

We found no evidence that either antimicrobial scrub product decreased bacterial contamination of HCWs' uniforms or skin after an 8-hour workday.

Newly cleaned physician uniforms and infrequently washed white coats have similar rates of bacterial contamination after an 8-hour workday: a randomized controlled trial

BACKGROUND

Governmental agencies in the United Kingdom and Scotland have recently instituted guidelines banning physicians' white coats and the wearing of long-sleeved garments to decrease nosocomial transmission of bacteria.

OBJECTIVE

Our aim was to compare the degree of bacterial and methicillin-resistant Staphylococcus aureus contamination of physicians' white coats with that of newly laundered, standardized short-sleeved uniforms after an 8-hour workday and to determine the rate at which bacterial contamination of the uniform ensued.

DESIGN

The design was a prospective, randomized controlled trial.

SETTING

The setting was a university-affiliated public safety-net hospital.

PARTICIPANTS

One hundred residents and hospitalists on an internal medicine service participated.

INTERVENTION

Subjects wore either a physician's white coat or a newly laundered short-sleeved uniform.

MEASUREMENTS

Bacterial colony count and the frequency with which methicillin-resistant Staphylococcus aureus was cultured from both garments over time were measured.

RESULTS

No statistically significant differences were found in bacterial or methicillin-resistant Staphylococcus aureus contamination of physicians' white coats compared with newly laundered short-sleeved uniforms or in contamination of the skin at the wrists of physicians wearing either garment. Colony counts of newly laundered uniforms were essentially zero, but after 3 hours of wear they were nearly 50% of those counted at 8 hours.

CONCLUSIONS

Bacterial contamination occurs within hours after donning newly laundered short-sleeved uniforms. After 8 hours of wear, no difference was observed in the degree of contamination of uniforms versus infrequently laundered white coats. Our data do not support discarding long-sleeved white coats for short-sleeved uniforms that are changed on a daily basis.

Detection of methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci on the gowns and gloves of healthcare workers

OBJECTIVE

To assess the rate of and the risk factors for the detection of methicillin-resistant S. aureus (MRSA) and vancomycin-resistant enterococci (VRE) on the protective gowns and gloves of healthcare workers (HCWs).

METHODS

We observed the interactions between HCWs and patients during routine clinical activities in a 29-bed medical intensive care unit at the University of Maryland Medical Center, an urban tertiary care academic hospital. Samples for culture were obtained from HCWs' hands prior to their entering a patient's room, from HCWs' disposable gowns and gloves after they completed patient care activities, and from HCWs' hands immediately after they removed their protective gowns and gloves.

RESULTS

Of 137 HCWs caring for patients colonized or infected with MRSA and/or VRE, 24 (17.5%; 95% confidence interval, 11.6%-24.4%) acquired the organism on their gloves, gown, or both. HCW contact with the endotracheal tube or tracheostomy site of a patient (P < .05), HCW contact with the head and/or neck of a patient (P < .05), and HCW presence in the room of a patient with a percutaneous endoscopic gastrostomy and/or jejunostomy tube (P < .05) were associated with an increased risk of acquiring these organisms.

CONCLUSIONS

The gloves and gowns of HCWs frequently become contaminated with MRSA and VRE during the routine care of patients, and particularly during care of the patient's respiratory tract and any associated indwelling devices. As part of a larger infection control strategy, including high-compliance hand disinfection, they likely provide a useful barrier to transmitting antibiotic-resistant organisms among patients in an inpatient setting.

Screening for extended-spectrum beta-lactamase-producing Enterobacteriaceae among high-risk patients and rates of subsequent bacteremia

BACKGROUND

Bloodstream infections due to extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae have been associated with increased hospital costs, length of stay, and patient mortality. However, the role of routine inpatient surveillance for ESBL colonization in predicting related infection is unclear.

METHODS

From 2000 through 2005, we screened 17,872 patients hospitalized in designated high-risk units for rectal colonization with vancomycin-resistant enterococci and ESBL-producing Enterobacteriaceae using a selective culture medium. In patients with a bloodstream infection due to ESBL-producing Enterobacteriaceae (ESBL-BI) during the study period, surveillance results were evaluated for evidence of antecedent ESBL-producing Enterobacteriaceae colonization.

RESULTS

The rate of ESBL-producing Enterobacteriaceae colonization doubled during the 6-year study period, increasing from 1.33% of high-risk patients in 2000 to 3.21% in 2005. Among patients with ESBL-producing Enterobacteriaceae colonization, 49.6% also carried vancomycin-resistant enterococci. The number of ESBL-BIs increased >4-fold in 5 years, from 9 cases in 2001 to 40 cases in 2005. Of 413 patients colonized with ESBL-producing Enterobacteriaceae, 35 (8.5%) developed a subsequent ESBL-BI. Of concern, more than one-half of all ESBL-BIs occurred in patients who were not screened. These 56 patients received a diagnosis of ESBL-BI in the emergency department, when hospitalized in low-risk medical units, or at transfer from an acute or long-term health care facility.

CONCLUSIONS

Colonization with ESBL-producing Enterobacteriaceae is increasing at a rapid rate, and routine rectal surveillance for ESBL-producing Enterobacteriaceae may have clinical implications. However, in our experience, over one-half of patients with an ESBL-BI did not undergo screening through our current surveillance measures. As a result, targeted screening for ESBL-producing Enterobacteriaceae among additional patient populations may be integral to future ESBL-BI prevention and management efforts.

Risk of environmental and healthcare worker contamination with vancomycin-resistant enterococci during outpatient procedures and hemodialysis

OBJECTIVE

To assess the risk of environmental and healthcare worker (HCW) contamination with vancomycin-resistant enterococci (VRE) during outpatient procedures performed on fecally continent patients currently colonized with VRE (cVRE) or previously colonized with VRE (pVRE).

DESIGN

Observational study.

SETTING

Outpatient consultation and radiology rooms and the hemodialysis unit in a university teaching hospital.

PATIENTS

Fecally continent cVRE and pVRE patients.

INTERVENTIONS

Both cVRE and pVRE patients attended standardized mock outpatient consultations and routine hemodialysis sessions in an area that had been thoroughly cleaned and microbiologically confirmed to be free of VRE contamination. After each session, the patient, environment, and participating HCW were tested for VRE contamination.

RESULTS

Fourteen cVRE patients participated in 49 mock outpatient consultation sessions and radiology sessions or 26 actual hemodialysis sessions, and 7 pVRE patients participated in 28 outpatient consultation sessions. Sessions with cVRE patients had higher rates of contamination of the environment (chair cultures were positive for VRE in 36% of outpatient consultation sessions, 58% of hemodialysis sessions; couch cultures were positive in 48% of outpatient consultation sessions, 42% of radiology sessions, and 45% of hemodialysis sessions), contamination of HCW gowns (gown cultures were positive in 20% of outpatient consultation sessions, 4% of radiology sessions, and 30% of hemodialysis sessions), and contamination of patients' own hands (hand cultures were positive in 36% of outpatient consultation sessions, 25% of radiology sessions, and 54% of hemodialysis sessions). Overall, contamination rates associated with pVRE patients attendance at outpatient consultations were 12% of those noted for cVRE patients (odds ratio, 0.10; 95% confidence interval, 0.03-0.42; P = .001).

CONCLUSIONS

Given the nature of the contamination risk posed by fecally continent cVRE patients undergoing outpatient procedures, infection control measures should focus on effective HCW and patient hand hygiene and chair and couch cleaning, to minimize transmission of VRE.

Active surveillance reduces the incidence of vancomycin-resistant enterococcal bacteremia

The impact of active surveillance of patients at risk for infection with vancomycin-resistant enterococci (VRE) was examined, and VRE bacteremia rates and the degree of VRE clonality in 2 similar neighboring hospitals were compared. Hospital A did not routinely screen patients for VRE rectal colonization; hospital B actively screened high-risk patients. Retrospective observations were made over the course of 6 years, beginning when initial VRE bloodstream isolates were recovered at each institution. The rate of VRE bacteremia was 2.1-fold higher at hospital A, and the majority of hospital A isolates were clonally related: 4 clones were responsible for infection in >75% of patients with VRE bacteremia, and isolates from 30% of patients were from the most common clone. The 4 most common clones at hospital B were responsible for infection in 37% of patients, and isolates from 14.5% of patients were from the most common clone. Lower VRE bacteremia rates and a more polyclonal population, representing less horizontal transmission, may result from routine screening of patients who are at risk for VRE and prompt contact isolation of colonized individuals.

Patient colonization and environmental contamination by vancomycin-resistant enterococci in a rehabilitation facility

OBJECTIVES

To determine the frequency of environmental contamination in patient and common-use rooms and patient colonization by vancomycin-resistant enterococci (VRE).

DESIGN

Cross-sectional study.

SETTING

A 146-bed rehabilitation facility.

PARTICIPANTS

Rectal cultures were collected from 74 (80%) of 93 patients. Environmental cultures were obtained from surfaces in 15 patient rooms (5 floors) and common-use areas on 8 floors.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Gastrointestinal colonization of patients and environmental contamination of surfaces by VRE.

RESULTS

VRE was detected from 13 (18%) of 74 patients and 32 (10%) of 319 surfaces. The frequency of positive environmental cultures varied by location; cultures were more likely to be positive in patient rooms (15%), followed by common areas on patient floors (9%) and common areas separate from patient floors (1.3%). Surfaces were more likely to be positive in rooms with a VRE-colonized patient (24%), compared with rooms in which patient colonization status was unknown (13%, P=.13) or the patient was not colonized (0%, P=.002). Surfaces were more likely to be contaminated in a room that housed an incontinent compared with continent patients (22% vs 7%, P=.01).

CONCLUSIONS

Although environmental contamination by VRE was common in patient rooms, contamination of common-use areas separate from patient floors was infrequent. Despite use of common-use areas by colonized patients, isolation practices at this facility appear to have minimized environmental surface contamination in these areas.

Contamination of the clinical microbiology laboratory with vancomycin-resistant enterococci and multidrug- resistant Enterobacteriaceae: implications for hospital and laboratory workers

We surveyed environmental surfaces in our clinical microbiology laboratory to determine the prevalence of vancomycin-resistant enterococci (VRE) and multidrug-resistant Enterobacteriaceae (MDRE) during a routine working day. From a total of 193 surfaces, VRE were present on 20 (10%) and MDRE were present on 4 (2%) of the surfaces tested. In a subsequent survey after routine cleaning, all of the 24 prior positive surfaces were found to be negative. Thus, those in the laboratory should recognize that many surfaces may be contaminated by resistant organisms during routine processing of patient specimens.